what babylonian god conferred immortality on utnapishtim and hiw wife out of remorse for causing the great food

Enlil

Explanation:

Enlil was the Sumerian god in ancient Mesopotamian who was associated with air, wind, earth, and storms. Enlil was a powerful god than any other deities and eventually worshiped as King of the Gods. Enlil sent the flood to destroy the humans, who made too much noise. Utnapishtim and his wife survive the flood. Enlil gave immortality as a reward for Utnanpishtim loyalty to the gods.